1. Field of the Invention
The present invention relates to a liquid crystal panel, and more particularly, to a liquid crystal-on-silicon (LCoS) panel utilizing one or multiple spacer walls and one-drop-fill technology.
2. Description of the Prior Art
Liquid crystal-on-silicon (LCoS) micro-display panel is arguably the heart of the reflective LCoS projectors and rear-projection televisions. The LCoS micro-display devices are tiny, less expensive, and have high resolution. As known in the art, the difference between a LCoS micro-display and a conventional thin film transistor-liquid crystal display (TFT-LCD) is materials used for forming substrates. Both of a cover and a backplane are made of glass in a TFT-LCD, nevertheless, the cover in a LCoS display is made of glass, but the backplane in a LCoS display is a semiconductor silicon substrate. Therefore, a LCoS process combines LCD techniques and complementary metal-oxide semiconductor (CMOS) processes.
Please refer to FIG. 1 and FIG. 2, wherein FIG. 1 is a schematic top view of a LCoS panel 10 according to the prior art and FIG. 2 is a schematic cross-sectional view of the LCoS panel 10 taken along line I-I of FIG. 1. The prior art LCoS panel 10 comprises a silicon substrate 12 used as a backplane and a glass substrate 16 being composed of, for example, indium tin oxide (ITO) glass. The silicon substrate 12 further comprises a plurality of pixel arrays (not explicitly shown) formed on its display active region 14. A liquid crystal layer 18 is sealed between the silicon substrate 12 and the glass substrate 16. Spherical spacers 22 of approximately equal size are disposed between the silicon substrate 12 and the glass substrate 16. In addition, a plurality of bonding pads 122 are formed on the longer side of the silicon substrate 12 used for soldering up the backplane and the cover in subsequent processes.
In LCD devices, the thickness of the liquid crystal layer 18, or the cell gap (i.e., the space between a transparent conducting substrate and a semiconductor substrate) has to be precisely controlled to a specific value so as to ensure the display performance. In order to maintain the cell gap, plastic beads, glass beads or glass fibers are normally interposed between two liquid crystal display substrates and used as spacers. Thus, this cell gap is defined by the spacer height. In a conventional LCD process, the spacers are positioned by spraying, so the positions between the two liquid crystal display substrates cannot be controlled accurately. Consequently, the display performance of the liquid crystal display device is affected due to light scattering by the spacers that are present in the light transmitting regions. Furthermore, the spacers tend to be mal-distributed so that the display performance in portions of the LCD with spacers bunched is impaired, and the uniformity of the cell gap cannot be precisely maintained.
According to the prior art, seal glue 20 is applied to the periphery of the display active area 14 of the silicon substrate 10. The seal glue 20 has a slit or break in it for liquid crystal injection in the subsequent processes. The prior art LCoS panel 10 has a drawback in that the design width of the seal glue 20 is about 2000 micrometers and the design width is about 500 micrometers, which occupy a large chip surface area. Further, in the traditional LC injection method, the cell will be vacuum filled by capillary attraction after the glass substrate 16 and the silicon substrate 12 are assembled. Such injection method has the drawbacks of wasting time and liquid crystal material.